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Biomedical subjects

K C Chou

Publications and source records attributed to K C Chou.

134 records · Page 8Linked to original sources
PubMed1980

Graphical rules for enzyme-catalysed rate laws.

Two graphical rules for calculating the reaction rates of steady-state enzyme-catalysed systems are presented. According to Rule 1, the number of non-zero terms can be easily calculated, which is useful to check the results and avoid mistakes. Rule 2 provides a new graphical method, which will be much more effective than the existing methods in dealing with complicated problems. In addition, during the process of deriving Rule 1, the mathematical principles of the Wong-Hanes structural rule have been naturally obtained too.

Enzymes↗
PubMed1980

Diffusion-controlled effects in reversible enzymatic fast reaction systems--critical spherical shell and proximity rate constant.

In this paper the diffusion-controlled effects in reversible enzyme fast reaction systems have been discussed. The main results are as follows: 1) An expression for the relation between the proximity second-order rate constant and the usual experimental second-order rate constant has been presented. From this expression we can see that the two kinds of rate constants are generally not equal unless the reaction proceeds very slowly (in comparison with the corresponding diffusion limit). 2) A new joint relation has been given between the theoretical calculated results and the experimentally measured ones for the activation energy. It has been pointed out that, for the reaction systems discussed here, it would no longer be valid to adopt the absolute reaction rate theory to calculate the activation energy as done commonly. 3) A formula has been given to calculate the upper limit obtainable possibly by experiments for the second-order rate constants in the reversible enzymatic fast reaction system. According to this formula, the value of such an upper limit is related not only to the diffusion coefficients of reacting molecules, the size of active surface, and the like, but also to the ratio of the concentration of product molecules to that of the substrate molecules at the equilibrium of the reaction system. Furthermore, the reversible enzymatic fast reaction system with multi-substrate and multi-product has been discussed, and a general equation for calculating the degree of reaction flow derived as well.

Diffusion↗
PubMed1980

The critical spherical shell in enzymatic fast reaction systems.

As we go more deeply into the theoretical analysis and actual calculations for enzymatic fast reaction systems, the concept of the critical shell would naturally be confronted with. In this paper, a formula is presented to estimate the thickness of the critical shell. An on such a basis, we have made calculations and discussed the influences of various factors such as short-range force, long-range force, activation energy and cavity-active site upon the thickness of the critical spherical shell.

Binding Sites↗
PubMed1980

A new schematic method in enzyme kinetics.

A new schematic method is presented which, in simplifying the calculation for complex enzymedcatalyzed mechanisms, is extraodinarily efficacious in comparison with the exiting schematic methods.

Enzymes↗
PubMedDate not supplied

Effects of zearalenone and/or tamoxifen on swine and mink reproduction.

Tamoxifen (TAM), which binds to estrogen receptors and can act as an estrogen antagonist, was incorporated into the diets of swine and mink to determine if it would ameliorate the effects of the estrogenic mycotoxin zearalenone (ZEN). Sows and female mink were fed diets containing 2 ppm (swine) or 20 ppm (mink) ZEN and/or 10 ppm TAM from day 30 of gestation through weaning (swine) or from 2 months prior to breeding through weaning (mink). The diets containing ZEN and/or TAM did not adversely affect reproduction in the sows. Although some hyperestrogenic effects on testes, uterine and ovarian weights were observed in the F1 piglets at 21 days of age, subsequent breeding performance was not affected. All the female mink exposed to ZEN mated, but only 25% whelped. No mink fed TAM (singly or in combination with ZEN) mated. Necropsy of these unmated females fed TAM revealed consistent severe pyometra. Histological examination of the reproductive tracts of the ZEN, TAM and ZEN + TAM-treated mink showed similar alterations, including ovarian follicular atrophy and degeneration, and mild to severe uterine atrophy, pyometra and endometritis. The results of these studies indicate that TAM was not effective in ameliorating the hyperestrogenic effects of ZEN in swine and mink, but rather it acted as an estrogen agonist.

Animals↗
PubMedDate not supplied

A model for structure-dependent binding of Congo red to Alzheimer beta-amyloid fibrils.

The cytotoxic A beta fibril is a logical candidate for the entity causing the initiating damage to neurons in Alzheimer's disease and Down's syndrome. We have derived a model of binding for the dye molecule, Congo red (CR), to a beta-sheet structure of beta-amyloid (1-42). This model is based on the crystal coordinates of CR binding to porcine insulin fibrils from Turnell and Finch. Intact insulin is composed of protein dimers and X-ray diffraction studies show that CR intercalates between two insulin monomers at an interface formed by a pair of antiparallel beta-strands. The intercalation of CR has disrupted the four main-chain hydrogen bonds between the two beta-strands, but they are still tethered with each other through new hydrogen bonds with the CR nitrogen atoms. The CR molecule has been aligned along the homologous stretch of amino acids in Alzheimer beta peptide (two molecules in antiparallel distorted or pseudo beta-sheet conformation) using the crystal coordinates from the Turnell-Finch paper to arrive at a putative structure for CR binding to Alzheimer's amyloid fibrils.

Algorithms↗
PubMedDate not supplied

The quantitative relations between diffusion-controlled reaction rate and characteristic parameters in enzyme-substrate reaction systems. I. Neutral substrates.

With the development of techniques for studying fast reactions, we are confronted with some experimental observations which, according to the classical diffusion-controlled reaction theory based on the assumption of pherical symmetry, will lead to paradoxical consequences. Recently, some investigators have attempted to present a theory of non-spherically symmetric diffusion-controlled reaction. Owing to the difficulty in mathematics, only the formal discussion has been given, and the numerical results have not yet been reported. The combination between enzyme and substrate is not only non-spherically symmetric, but also related to the force field existing between the reacting molecules. In the previous article we introduced the spatial factor and the force field factor and derived a general equation for these reaction systems. We present in this article a general method for finding the numerical solution of the above equation. With the numerical results obtained by this method we may interpret the experimental facts which can not be explained from the viewpoint of the classical diffusion-controlled reaction theory. In order to examine more closely the kinetic behaviour of enzyme-substrate reaction systems, we defined several characteristic parameters. The quantitative relation between these parameters and the rate of diffusion-controlled reaction has been discussed.

Binding Sites↗